(1) Field of the Invention
The present invention relates to a method and apparatus for determining the degree of interlacing of individual filaments in interlaced multifilament yarns.
In the instant specification and claims, by the term "interlaced multifilament yarn" is meant not only an interlaced multifilament yarn which has been processed by an interlacing machine and formed into a yarn package, but also an interlaced multifilament yarn which has been processed by an interlacing machine and is running toward a yarn package forming device for forming it into a yarn package. The term "interlaced multifilament yarn" is used in a very wide sense so that the conventional interlaced multifilament yarn made from such material as polyester, polyamide, acetate multifilament yarn, etc., is covered.
(2) Description of the Prior Art
The degree of interlacing, which is expressed by the number of entanglements along the unit length of yarn, or the coherency factor, which is expressed by the average yarn length between two entanglements, is an important factor for defining the quality of interlaced multifilament yarns. As the method for determining such characteristics, there has been adopted the hook-drop test method. According to this method, a contact probe is inserted into the yarn, by moving the contact probe or yarn, the entanglement is detected by the force or displacement the probe undergoes on passage through the entangled portion and characteristics such as the degree of interlacing are thus determined. An apparatus for performing this hook-drop test automatically is disclosed in the specification of U.S. Pat. No. 3,290,932.
As will be apparent from the above-mentioned measurement principle, in order to detect entanglements assuredly according to the hook-drop test method, it is necessary to move the yarn or contact probe at a low speed. Therefore, this method involves a defect that the measurement efficiency is very low. For example, the measurement is ordinarily conducted at a running speed lower than 5 m/min, and more than 1 minute is necessary for completing the measurement on a yarn sample having a length of 5 to 10 m.
As pointed out above, the degree of interlacing is a very important factor for evaluating the quality of interlaced yarns. Accordingly, at the inspection step in the interlaced yarn manufacturing process, a great number of sample packages should be picked up from products and tested for quality control. Since the number of samples to be tested is very large and the measurement operation now adopted is very troublesome, there is brought about a disadvantage that the measurement is labor-consuming. Further, at the inspection step, only a very minute portion of a sampled product package is tested. Accordingly, a temporary and abnormal change of the interlacing degree during production cannot be detected. This is another defect of the conventional test method.